1261. Find Elements in a Contaminated Binary Tree

Medium
Given a binary tree with the following rules:
  1. 1.
    root.val == 0
  2. 2.
    If treeNode.val == x and treeNode.left != null, then treeNode.left.val == 2 * x + 1
  3. 3.
    If treeNode.val == x and treeNode.right != null, then treeNode.right.val == 2 * x + 2
Now the binary tree is contaminated, which means all treeNode.val have been changed to -1.
Implement the FindElements class:
  • FindElements(TreeNode* root) Initializes the object with a contaminated binary tree and recovers it.
  • bool find(int target) Returns true if the target value exists in the recovered binary tree.
Example 1:
​
​
Input
["FindElements","find","find"]
[[[-1,null,-1]],[1],[2]]
Output
[null,false,true]
Explanation
FindElements findElements = new FindElements([-1,null,-1]);
findElements.find(1); // return False
findElements.find(2); // return True
Example 2:
​
​
Input
["FindElements","find","find","find"]
[[[-1,-1,-1,-1,-1]],[1],[3],[5]]
Output
[null,true,true,false]
Explanation
FindElements findElements = new FindElements([-1,-1,-1,-1,-1]);
findElements.find(1); // return True
findElements.find(3); // return True
findElements.find(5); // return False
Example 3:
​
​
Input
["FindElements","find","find","find","find"]
[[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]]
Output
[null,true,false,false,true]
Explanation
FindElements findElements = new FindElements([-1,null,-1,-1,null,-1]);
findElements.find(2); // return True
findElements.find(3); // return False
findElements.find(4); // return False
findElements.find(5); // return True
Constraints:
  • TreeNode.val == -1
  • The height of the binary tree is less than or equal to 20
  • The total number of nodes is between [1, 10^4]
  • Total calls of find() is between [1, 10^4]
  • 0 <= target <= 10^6

解題

/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
type FindElements struct {
tree *TreeNode
}
​
​
func Constructor(root *TreeNode) FindElements {
root.Val = 0
createTree(root)
return FindElements{ tree: root }
}
​
func createTree(root *TreeNode) {
if root == nil { return }
​
if root.Left != nil {
root.Left.Val = 2 * root.Val + 1
}
​
if root.Right != nil {
root.Right.Val = 2 * root.Val + 2
}
​
createTree(root.Left)
createTree(root.Right)
}
​
func (this *FindElements) Find(target int) bool {
return find(this.tree, target)
}
​
func find(root *TreeNode, target int) bool {
if root == nil { return false }
if root.Val == target { return true }
​
return find(root.Left, target) || find(root.Right, target)
}
​
​
/**
* Your FindElements object will be instantiated and called as such:
* obj := Constructor(root);
* param_1 := obj.Find(target);
*/